Protected gap closing in Josephson junctions constructed on Bi₂Te₃ surface

On the road of searching for Majorana zero modes(MZMs) in topological insulator-based Josephson junctions, a highly-sought signature is the protected full transparency of electron transport through the junctions due to the existence of the MZMs, associated with complete gap closing between the electronlike and holelike Andreev bound states (ABSs). We fabricated Pb-Bi₂Te₃-PbJosephson junctions and developed the method of using nonsuperconducting Pd electrodes to detect the ABS spectra in the junctions area. We generalized the Blonder-Tinkham-Klapwijk theory to describe the measured contact resistance of the Pd-Bi₂Te₃ interface. Our results provide direct experimental evidence of complete gap-closing and full transparent transport in single Josephson junctions constructed on the surface of Bi₂Te₃.

[1] Zhaozheng, Lyu, Yuan Pang, Junhua Wang, et al., Phys. Rev. B 98, 155403 (2018)